A thyristor is a four-layer latching switching device having an anode and a cathode for current flow and a gate for switching the device from a blocking state to a conducting state, and vice versa. A control signal applied to the gate causes the device to “latch” into a conductive state in which current can flow freely between the anode and cathode of the device. The device remains in the conductive state even after the control signal is removed. A second control signal, opposite in polarity to the first control signal, switches the device back into the “off” or blocking state. The design of optically triggered wide bandgap thyristors is generally known in the art. For example, U.S. Pat. No. 6,770,911 entitled “Large Area Silicon Carbide Devices,” assigned to the assignee of the present application, describes the design and manufacture of optically triggered silicon carbide thyristors. U.S. Pat. No. 6,770,911 is hereby incorporated herein by reference as if set forth in its entirety.
Other silicon carbide thyristors are described, for example, in U.S. Pat. No. 5,539,217, the disclosure of which is incorporated herein by reference as if set forth fully. The thyristors described in the '217 patent are three terminal devices having a gate and one of an anode or a cathode on a first side of the device and the other of the anode and the cathode on the opposite side of the device. Such silicon carbide thyristors may exhibit improved power handling capabilities over similar silicon thyristors.
Light activated silicon thyristors have been utilized in high power applications. For example, optically triggered parallel lateral thyristors are described in U.S. Pat. No. 4,779,126, the disclosure of which is incorporated herein by reference as if set forth fully. Light-activated (i.e., optically triggered) thyristors having an integrated light source and a silicon carbide active layer have been described in U.S. Pat. No. 5,663,580, the disclosure of which is incorporated herein by reference as if set forth fully. Other optically triggered wide bandgap devices are illustrated in U.S. Publication No. 2006/0261876, the disclosure of which is incorporated herein by reference as if set forth fully.